Protective holder for electric discharge devices



April 30, 1946. A. A. OLSEN PROTECTIVE HOLDER FOR ELECTRIC DISCHARGE DEVICES v Filed March 13, 1941 Attorney.

Patented Apr. 30, 1946 PROTECTIVE HOLDER FOR ELECTRIC DISCHARGE DEVICES Arthur A. Olsen, Pittsfield, Mass., assignor to General Electric Company, a corporation of New York Application March 13, 1941, Serial No. 383,093

3 Claims.

The present invention relates to protective holders for electric discharge devices and, while it isnot necessarily so limited, it is particularly adaptable for mounting vacuum gap lightning arresters within transformer tanks.

Electric discharge devices of the type having a plurality of electrodes sealed within an evacuated glass envelope are relatively fragile units and are generally mounted only in such locations where they are not apt to be subjected to any blows or externally applied forces. In certain instances, however, it is expedient to mount such a discharge device in a hazardous location with special protective means provided for preventing accidental injury to the device. In the usual arrangement, the protective means is in the form of a guard which is arranged adjacent the device, but while such means may prevent the device from being struck, as with a wrench, the device may still suffer injury through a force transmitted through the leads or support.

It is, therefore, an object of the present invention to provide a new and improved protective holder for a relatively fragile element such as an electric discharge device.

For a consideration of what I believe to be novel and my invention attention is directed to the following description and the claims appended thereto taken in connection with the accompanying drawing in which Fig. 1 is a view in perspectiveof a portion of a transformer illustrating a typical lightning arrester installation with a holder of the present invention; Fig. 2 is an enlarged cross sectional view through the holder shown in Fig. 1; Fig. 3 is an exploded view in perspective more clearly illustrating certain parts of the holder; and Fig. 4 is a cross sectional view of Fig. 2 along line 44.

The holder of the present invention will be described as adapted for mounting a vacuum gap lightning arrester within a distribution type transformer tank though other applications for the holder will readily occur to one skilled in the art. The present trend in distribution transformer design is to mount as much of the auxiliary apparatus within the tank as possible so as to provide a substantially completely self-contained unit. Thus there may be mounted within the tank in addition to the usual terminal board, such apparatus as a ratio adjuster switch, a plurality of overload protective fuses, a circuit breaker, a temperature indicating mechanism as well as one or more lightning arresters. In servicing such a transformer it is frequently necessary for the lineman to insert a wrench or some other tool into the tank for the purpose of making adjustments or replacements. Should the implement slip in the hands of the lineman and strike against one of the lightning arresters, even with a light blow, it might crack or break the fragile glass envelope. Even though the glass envelope might not be destroyed, a relatively sharp blow or force applied either to the support or to a lead connected to one of the terminals of the discharge device might cause a variation in the spacing between the electrodes thereof, which is initially rather critically adjusted.

Referring to Fig. l, a transformer is shown comprising a housing I0 having arranged therein a transformer unit including winding l I and core structure [2. Secured to an upper core clamp I3 is an angle bracket it having a threaded hole therein for cooperatively receiving a lower stud of an electric discharge device holder 15. An upper terminal stud of the holder I5 is connected by a lead 16 to a line terminal of the transformer.

The electric discharge device holder l5. shown more clearly in Fig. 2, comprises a longitudinal tubular or cylindrical insulating member 2! within which is mounted the electric discharge device 22. The electric discharge device 22 in this instance is a vacuum gap type lightning arrester of the form further described in the Patent No. 1,906,602, issued to Albert W. Hull, May 2, 1933, and assigned to the General Electric Company, the assignee of the present application. The lightning arrester includes a pair of electrodes 24 and 25 enclosed within an evacuated glass envelope 26 and connected to terminal studs 21 and 28 extending axially from the opposite ends of the device. The insulating member 2| has an inner diameter somewhat greater than the outer diameter of the device 22 and a somewhat greater overall length. The insulating member 2| is also preferably of a relatively tough and durable insulating material, such as fiber, so that it can withstand relatively sharp accidental blows without appreciable deformation.

Secured to the opposite ends of the tubular insulating member 2| as by screws 29 are metal caps 3| and 32, respectively, which are provided with axially extending terminal studs 33 and 34, respectively. The end terminals of the electric discharge device are connected to corresponding terminal studs of the holder by means of similar spring strips 35 and 35 extending between the terminals 21 and 28 of the device 22 and the terminal studs 33 and 34 of the holder l5, respectively. The spring strips preferably comprise a plurality of legs arranged symmetrically as regards the common axis of the various terminal studs forming parallel conductive paths between the interconnected terminals. As shown in Fig. 3, the spring strip 35 is provided with a hole 38 intermediate its integrally connected ends for cooperatively receiving one of the terminals, for example 27, of the discharge device 22. The ends of the strip 35 are adapted to extend through or be brought through the diametrically opposite openings 39 and 40 of the end cap and folded over the end wall thereof, holes 4| and 42 being provided for fitting over the terminal stud. The portions of the strip between the holder stud and the device terminal stud 2! are bent inwardly as indicated at 43 and 44 so as to add to the resiliency of the mounting. The strips are held firmly in place upon the various terminal studs by suitable nuts. Washers 46 are provided on opposite sides of the spring strips on the terminals of the discharge device which preferably have projecting corners to facilitate the assembly of the strips in a definite relationship in spite of their tendency to revolve on the terminals as the nuts are tightened. The corners of the washers 46, furthermore, project beyond the sides of the glass envelope of the device 22, as shown more clearly in Fig. 4, so as to assure that the glass envelope will be kept spaced from the wall of the tube 2 I. Any side blows against the holder will be transmitted to the discharge device, if at all, through the corners of the washers to the heavy terminal parts.

In order further to prevent the possibility of one of the terminal studs 21 and 28 of the dis- W charge device from coming into contact with the inner end of either of the studs 33 or 34, respectively, by a relative longitudinal movement of the device 22 within the holder pads 48 and 49 of a rubber-like resilient material impervious to oil or other insulating liquid with which the transformer is filled are arranged over the upper end and lower end respectively of the tubular insulating member 2| and extending between the adjacent terminal members. The dimensions of the pads 48 and 49 are such that their ends contact the inside surface of the caps so as to frictionally hold the pads in place. Also the legs of the spring strips are bent inwardly sufficiently so that the portions 43 and 44 may cooperate with the pad 48 to prevent it from dropping below the terminal 2?. Suitable openings may be provided through the insulating tube 2| for facilitating visual inspection of the device contained therein.

The electric discharge device is first mounted within the holder with reasonable care after which, due to the fact that the tubular insulating enclosure is mechanically strong, it may be subjected to considerable rough treatment without injury thereto. The device may be mounted within the holder 2| by first attaching the spring strips and 36 to their respective terminals 21 and 28. The ends of the lower strip 35 are brought through the openings in the metal cap and the stud 34 passed through the holes in the ends of the strips. The device 22 is then inserted into the tube 2| and the cap 32 attached to the adjacent end of the tube by the screws 29. The cap 3| is placed on the other end of the cylinder 2| by passing the legs of the strip 35 through the openings 39 and 43. The ends of the legs are then folded over with the stud 33 projecting through the holes 4| and 42. A tool may then be inserted in each end of the tube 2| for bending the legs of the strips 35 and 36 inwardly. Thus the device may be secured to the support simply by grasping the upper end cap of the holder and rotating it to screw the lower stud 34 into the cooperatively threaded hole provided in the angle bracket M. In order that the end caps will withstand such a transmission of torsional force from one to the other through the tubular insulating member, the end caps should be securely fastened in place as by a sufiicient number of screws 29. The lead l6 may also be secured to the upper stud 33 by a wrench with a considerable force applied thereto without danger of injuring the discharge device enclosed within the holder.

Under heavy electrical discharges, the electromagnetic forces set up within each leg of the connections 35 and 35 are such as to cause these conductors to be aligned violently with the axis of the device. If the connection strips each consisted of a single leg, a sharp side thrust would be imparted to the vacuum gap at each discharge. By using connection strips of two legs arranged substantially symmetrically as regards the axis of the device, the mechanical forces exerted by the two legs during such discharges practically balance each other so that no appreciable resultant shock is transmitted to the vacuum gap.

Insulating liquid enclosed within the transformer tank may circulate freely through the tubular member 2| around the enclosed discharge device by virtue of the openings 39 and 48 provided in the opposite end caps. The device 22 being resiliently mounted within the holder will be substantially unaffected by sharp jolts given to the holder, as upon a wrench being dropped into the transformer tank or slipping from an adjacent nut during a servicing operation.

Having described the principle of my invention in what I consider to represent a preferred embodiment thereof, I desire to have it understood that the specific details shown are merely illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A holder for supporting a relatively fragile electrical device provided with a terminal com" prising, in combination, a cylinder in which the electrical device is located, a cap arranged at one end of said cylinder, said cap being provided with a terminal, resilient conductive means carried by said cap and adapted to be secured to the terminal of the electrical device for yieldingly supporting the device in said tube for movement toward and away from said cap, and a member of resilient material carried by said cap and being disposed between the cap and the terminal of the electrical device for engaging the terminal upon movement of the device toward said cap.

2. A holder for supporting in a dielectric fluid an electric discharge device having a relatively fragile envelope and a terminal extending from each of the opposite ends of the envelope comprising, in combination, a tubular insulating member surrounding and enclosing the electrical device, caps having terminal means carried by said member at each end thereof, and flexible conductive means carried by each of said caps, said conductive means being secured to the terminals of the electric device for supporting the device spaced from the inner wall of the tubular member and for movement toward and away from the end caps, said caps being provided with openings to allow free circulation of dielectric fluid through the caps and along the space between the electrical device and tubular member.

3. A holder for a relatively fragile electrical device having terminals extending from opposite ends thereof comprising; in combination, a tubular insulating member surrounding and enclosing the electrical device, caps having terminal studs carried by said member at each end thereof, said end caps being provided with openings spaced on opposite sides of said studs, strips of flexible spring material secured to the terminals of the electrical device, the ends of the strips extending through vthe openings in the corre sponding end caps and being fastened to the terminal studs for resiliently supporting the device within the tubular member.

ARTHUR A. OLSEN. 

